Studies in our laboratory will focus on four areas in the coming year. First, we propose to synthesize a radioactively labeled (125I) photoaffinity labeling analog of CCK-OP for use in defining the biochemical properties of the CCK receptor in the adult acinar cell and for use as a probe in determining appearance of CCK receptors in these developing pancreas. Second, we will examine, using biosynthetic labeling protocols and SDS-PAGE, the pattern of appearance of cell surface glycoproteins during embryonic pancreatic histogenesis. Additional studies using immunocytochemical approaches will follow changes in basal lamina and other connective tissue components during gland morphogenesis. Third, we plan to pursue studies on a differentiated rat acinar cell tumor with the aim or determining the potential role of basal lamina constituents in tissue disorganization in the neoplasm and of defining plasmalemmal components that may be responsible for interactions of cells with the extracellular matrix. Finally, studies will continue in an effort to label in situ the apical plasmalemma of the mature acinar cell with 125I for comparison with the membrane of the zymogen granule which specifically interacts with this plasmalemmal domain during exocytosis. Along the same line, we propose to identify the subcellular localization of proteins that are phosphorylated in the acinar cell during secretagogue stimulation of exocytosis.